System for a semiconductor fabrication facility and method for operating the same

ABSTRACT

An automatic cleaning unit for AMHS includes a plurality of sensors disposed on OHT rails. The sensors are configured to define a cleaning zone and to detect a location of an OHT vehicle. The automatic cleaning unit further includes a vacuum generator and a top cleaning part installed over the OHT rails in the cleaning zone. The top cleaning part is coupled to the vacuum generator. The vacuum generator is turned on to perform a vacuum cleaning operation when the sensors detect the OHT vehicle entering the cleaning zone.

PRIORITY CLAIM AND CROSS-REFERENCE

This patent is a divisional application of U.S. patent application Ser.No. 16/114,953 filed on Aug. 28, 2018, entitled of “SYSTEM FOR ASEMICONDUCTOR FABRICATION FACILITY AND METHOD FOR OPERATING THE SAME”,which application is hereby incorporated herein by reference.

BACKGROUND

Automated Material Handling Systems (AMHS) have been widely used insemiconductor fabrication facilities (“FABS”) to automatically handleand transport groups or lots of wafers between various processingmachines (“tools”) used in chip manufacturing. A typical FAB may includeone or more floors having a plurality of process bays includingprocessing tools and wafer staging equipment, which are interconnectedby the AMHS.

Each bay may include a wafer stocker, which includes multiple bins fortemporarily holding and staging a plurality of wafer carriers during thefabrication process. The wafer carriers may include standard mechanicalinterface (SMIF) pods which may hold a plurality of 200 mm (8 inch)wafers, or front opening unified pods (FOUPs) which may hold larger 300mm (12 inch) wafers. Stockers generally include a single mast roboticlift or crane having a weight bearing capacity sufficient for lifting,inserting, and retrieving single wafer carriers one at a time from thebins. The stocker holds multiple SMIF pods or FOUPs in preparation fortransporting a SMIF or FOUP to the loadport of a processing tool.

A semiconductor FAB may include numerous types of automated and manualvehicles for moving and transporting wafer carriers throughout the FABduring the manufacturing process. These may include, for example,automatic guided vehicles (AGVs), personal guided vehicles (PGVs), railguided vehicles (RGVs), overhead shuttles (OHSs), and overhead hoisttransports (OHTs). An OHT system automatically moves OHT “vehicles” thatcarry and transport wafer carriers, such as SMIF pods or FOUPs holdingmultiple wafers, from a processing or work tool or a stocker to theloadport of another tool or other apparatus in the FAB. The OHT systemmay be used to transport vehicles within each bay (intra-bay) or betweenbays (inter-bay). The OHT system also moves empty vehicles (i.e.,vehicles without a wafer carrier) to the tool loadport or otherapparatus for receiving and removing empty or full SMIF pods or FOUPsthat may contain wafers for further transport and/or processing in othertools.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It shouldbe noted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a schematic layout diagram of a system for the semiconductorfabrication facility, in accordance with some embodiments of the presentdisclosure.

FIG. 2 is a schematic drawing of a portion of the system according toaspects of the present disclosure in one or more embodiments.

FIG. 3 is a schematic drawing of a portion of an automatic cleaning unitaccording to aspects of the present disclosure in one or moreembodiments.

FIG. 4A is a schematic drawing of a portion of an automatic cleaningunit according to aspects of the present disclosure in one or moreembodiments.

FIG. 4B is a schematic drawing of a portion of an automatic cleaningunit according to aspects of the present disclosure in one or moreembodiments.

FIG. 5 is a flowchart representing a method for cleaning an OHT vehicleaccording to aspects of the present disclosure.

FIG. 6 is a flowchart representing a method for cleaning an OHT vehicleaccording to aspects of the present disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of elements and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or over a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofbrevity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper,” “on” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

As used herein, terms such as “first,” “second” and “third” describevarious elements, components, regions, layers and/or sections, but theseelements, components, regions, layers and/or sections should not belimited by these terms. These terms may be used only to distinguish oneelement, component, region, layer or section from another. The termssuch as “first,” “second” and “third” when used herein do not imply asequence or order unless clearly indicated by the context.

As used herein, the terms “approximately,” “substantially,”“substantial” and “about” are used to describe and account for smallvariations. When used in conjunction with an event or circumstance, theterms can refer to instances in which the event or circumstance occursprecisely as well as instances in which the event or circumstance occursto a close approximation. For example, when used in conjunction with anumerical value, the terms can refer to a range of variation of lessthan or equal to ±10% of the numerical value, such as less than or equalto ±5%, less than or equal to ±4%, less than or equal to ±3%, less thanor equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%,less than or equal to ±0.1%, or less than or equal to ±0.05%. Forexample, two numerical values can be deemed to be “substantially” thesame or equal if a difference between the values is less than or equalto ±10% of an average of the values, such as less than or equal to ±5%,less than or equal to ±4%, less than or equal to ±3%, less than or equalto ±2%, less than or equal to ±1%, less than or equal to ±0.5%, lessthan or equal to ±0.1%, or less than or equal to ±0.05%. For example,“substantially” parallel can refer to a range of angular variationrelative to 0° that is less than or equal to ±10°, such as less than orequal to ±5°, less than or equal to ±4°, less than or equal to ±3°, lessthan or equal to ±2°, less than or equal to ±1°, less than or equal to±0.5°, less than or equal to ±0.1°, or less than or equal to ±0.05°. Forexample, “substantially” perpendicular can refer to a range of angularvariation relative to 90° that is less than or equal to ±10°, such asless than or equal to ±5°, less than or equal to ±4°, less than or equalto ±3°, less than or equal to ±2°, less than or equal to ±1°, less thanor equal to ±0.5°, less than or equal to ±0.1°, or less than or equal to±0.05°.

Handling and transport of 300 mm wafers in correspondingly larger andheavier FOUPS creates efficiency challenges for the AMHS to maintainexpedient wafer flow between processing tools in the semiconductor FAB.In some embodiments, more than 8000 overhead hoist transport (OHT)vehicles are used. It is found that OHT vehicles have a tendency togenerate particles or debris due to friction between wheels/rollers andthe OHT rail. Such particles may fall down and potentially contaminatework tools and equipment that are delicate precision instruments andhave expensive high-precision electronic components, which demand anabsolutely clean environment in the facility during the conducting ofmanufacturing, processing and assembling procedures. In someembodiments, the particles caused by the movement of the OHT vehicleover an extended period of time may not be readily visible or noticeableupon falling from the overheard rail carrying the OHT, creatingcontaminated conditions in the facility. Such contamination isdeleterious to the quality and integrity of the wafer being manufacturedand threatens the functioning of work tools and equipment being employedbeneath the OHT rail or the OHT vehicles.

In some embodiments, the OHT vehicles are taken from the OHT rails,moved to an area for cleaning, and the particles are manually removed bya vacuum cleaner. After the OHT cleaning operation, the OHT vehicles areput back to the OHT rails. The manual cleaning is performed at specifiedand occasionally requested time intervals. Such manual OHT vehiclecleaning operations are time-consuming and sometimes unable to achieve arequired level of OHT vehicle cleanliness. For example, cleaning one OHTvehicle can require one hour. This results in manufacturing downtime andimpacting the profitability of the FAB. Furthermore, manual cleaningprocedures require extreme care in cleaning the OHT vehicles underrequisite standards of cleanliness.

The present disclosure therefore provides an automatic cleaning unit, asystem including automatic cleaning units and a method for cleaning theOHT vehicles automatically. The automatic cleaning unit can be adaptedto function on the OHT rails. In some embodiments, the automaticcleaning unit includes sensors to detect a location of the OHT vehicleand thus the automatic cleaning unit can be automatically turned on whenthe OHT vehicle is approaching or entering the automatic cleaning unit.A cleaning operation is then performed to remove particles from the OHTvehicles. Further, the automatic cleaning unit can also be automaticallyturned off when the cleaning operation is completed or after the OHTvehicle leaves the automatic cleaning unit. Further, the automaticcleaning unit includes vacuum cleaning equipment for removing particlesfrom the OHT vehicle from three directions.

FIG. 1 is a schematic layout diagram of a system 100 for thesemiconductor fabrication facility in accordance with some embodimentsof the present disclosure, FIG. 2 is a schematic drawing of a portion ofthe system 100 in accordance with some embodiments of the presentdisclosure, and FIG. 3 is a schematic drawing of a portion of the system100 in accordance with other embodiments of the present disclosure. Thesystem 100 is provided in a clean room of a semiconductor factory or thelike. In some embodiments, the system 100 can be provided in facilityhaving one or more floors, but the disclosure is not limited thereto.Referring to FIG. 1, the system 100 includes a network of OHT rails 110,a plurality of wafer processing or metrology tools 120, a plurality ofwafer stockers 130, a plurality of OHT vehicles 140, a plurality ofsensors 154 a and 154 b (shown in FIGS. 2 and 3) on the OHT rails 110,and a plurality of automatic cleaning units 150.

Referring to FIG. 1, the system 100 is usually organized into aplurality of bays 102 each including several of the wafer processing ormetrology tools 120. In some embodiments, each bay 102 may includeseveral tools 120 for performing various semiconductor manufacturing,testing, or metrology steps. Thus, the network of OHT rails 110 caninclude two types of transport loops: the inter-bay loop 112 a betweenthe bays 102, and the intra-bay loop 112 b between the processing tools120 of a single bay 102. In some embodiments, it is also possible thatthese two types of transport loops can be merged into one monolithicsystem with appropriate control and transfer mechanisms. In someembodiments, the inter-bay loop 112 a can be arranged over a centralcorridor or a central aisle 104, and the plurality of bays 102 (eachincluding the several tools 120) are arranged on opposing lateral sidesof the central aisle 104, as shown in FIG. 1, but the disclosure is notlimited thereto. Thus, the intra-bay loops 112 b are also arranged onthe opposite lateral sides of the central aisle 104, as shown in FIG. 1.In some embodiments, the OHT rails 110 are monorails that are affixed toand suspended from the ceiling of the clean room.

Each bay 102 may include a wafer stocker 130, which includes multiplebins for temporarily holding and staging a plurality of wafer carriersduring the fabrication process. The wafer carriers may include standardmechanical interface (SMIF) pods which may hold a plurality of 200 mm (8inch) wafers, or front opening unified pods (FOUPs) which may holdlarger 300 mm (12 inch) wafers. In some embodiments, the wafer stockers130 include a single mast robotic lift or crane having a weight bearingcapacity sufficient for lifting, inserting, and retrieving wafercarriers one at a time from the bins. The wafer stocker 130 holdsmultiple SMIF pods or FOUPs in preparation for transporting a SMIF orFOUP to the loadport of a processing tool.

Referring to FIGS. 1 to 3, the OHT vehicles 140 are movably mounted onthe OHT rails 110 along a moving direction. Each of the OHT vehicles 140is operable to transport the wafer carrier (not shown) through thesystem 100 for inter-bay or intra-bay movement. In some embodiments,each of the OHT vehicles 140 may be configured and structured to holdone wafer carrier at a given time and transport the wafer carrier in agenerally horizontal direction from one direction to another within eachbay 102 or between bays 102. As shown in FIGS. 2 and 3, each of the OHTvehicles 140 may include a wheeled trolley 142, which is configured tocomplement and cooperate with the OHT rails 110 for rolling movementalong the OHT rails 110. In other words, the OHT vehicles 140 aresuspended from the OHT rails 110 through the wheeled trolley 142. Insome embodiments, the wheeled trolley 142 may include a height H and awidth W. It should be understood that embodiments in which the OHT rails110 mate with the wheeled trolley 142 are not limited to any particularconfiguration so long as the OHT vehicles 140 are appropriatelysupported from the OHT rails 110 for rolling motion.

Referring to FIGS. 1 and 2, in some embodiments, the plurality of firstsensors 154 a and 154 b are disposed on the OHT rails 110 to detectlocations of the OHT vehicles 140. In some embodiments, the firstsensors 154 a and 154 b can include a laser sensor, a limit switch, atouch sensor, an ultrasonic sensor, a camera or any suitablemechanically actuated device, but the disclosure is not limited thereto.More importantly, the first sensors 154 a and 154 b are used to define aplurality of cleaning zones 106, and the automatic cleaning units 150are installed in the cleaning zones 106, respectively. In someembodiments, the cleaning zone 106 can be greater than the automaticcleaning unit 150, as shown in FIG. 1, but the disclosure is not limitedthereto. Still referring to FIG. 1, the automatic cleaning units 150 areseparated from each other by a distance, and the distance between twoautomatic cleaning units 150 is between approximately 500 m andapproximately 3000 m, but the disclosure is not limited thereto. In someembodiments, the distances between the automatic cleaning units 150 areidentical. In other embodiments, the distances between the automaticcleaning units 150 vary. In some embodiments, the first sensors 154 aand 154 b can include different functions, which will be describedbelow. In some embodiments, the automatic cleaning units 150 of thesystem 100 can further include a plurality of second sensors 156 a and156 b over the OHT rails 110. In some embodiments, the second sensors156 a and 156 b are disposed proximate to the cleaning zone 106, asshown in FIGS. 2 and 3. The second sensors 156 a and 156 b can include acamera, but the disclosure is not limited thereto. In some embodiments,the second sensors 156 a and 156 b can include different functions,which will be described below. In some embodiments, the system 100further includes a controller 160 (as shown in FIG. 1) in communicationwith the sensors 154 a and 154 b and the cleaning units 150 andcontrolling operations of the system 100, as will be describedhereinafter.

Referring to FIG. 2, in some embodiments, each of the automatic cleaningunits 150 includes the plurality of first sensors 154 a and 154 b, avacuum generator 158, a piping system 159 and a top cleaning part 152T.In some embodiments, the first sensors 154 a and 154 b can include alaser sensor, a limit switch, a touch sensor, an ultrasonic sensor, acamera or any suitable mechanically actuated device, but the disclosureis not limited thereto. The first sensors 154 a and 154 b are configuredto detect a location of the OHT vehicle 140. The top cleaning part 152Tis installed over the OHT rails 110 in the cleaning zone 106. Further,the top cleaning part 152T of the automatic cleaning unit 150 is spacedapart from the OHT rails 110 by a distance D1. In some embodiments, thedistance D1 between the top cleaning part 152T and the OHT rail 110 isgreater than the height H of the wheeled trolley 142 of the OHT vehicle140 such that the OHT vehicle 140 is allowed to pass through along amoving direction as shown in FIG. 2. Further, a size of the top cleaningpart 152T is substantially greater than that of the wheeled trolley 142of the OHT vehicle 140. In some embodiments, the top cleaning part 152Tis connected to the vacuum generator 158 by the piping system 159. Insome embodiments, ratio of an amount of the vacuum generators 158 and anamount of the automatic cleaning units 150 is 1:1, but the disclosure isnot limited thereto. In some embodiments, each automatic cleaning unit150 may include a vacuum generator 158. In some embodiments, two or morecleaning units may share one vacuum generator 158. In some embodiments,a high efficiency particulate air (HEPA) filter can be adopted in thevacuum generator 158 for preventing pollution to the environment, butthe disclosure is not limited thereto. In some embodiments, the vacuumgenerator 158 can include a pump, an ejector, etc. adapted to create thevacuum. In some embodiments, the piping system 159 includes a pluralityof branch pipes 159-1 and a main pipe 159-2. As shown in FIG. 2, theplurality of branch pipes 159-1 are connected to the top cleaning part152T, and the main pipe 159-2 connects the plurality of branch pipes159-1 to the vacuum generator 158.

Referring to FIG. 3, in some embodiments, each of the automatic cleaningunits 150 includes the plurality of first sensors 154 a and 154 b, thevacuum generator 158, the piping system 159, the top cleaning part 152Tand a pair of side cleaning parts 152S. The pair of side cleaning parts152S are coupled to the top cleaning part 152T. As shown in FIG. 3, thetop cleaning part 152T is installed over the OHT rails 110 in thecleaning zone 106, while the pair of side cleaning parts 152S areinstalled at two sides of the OHT rails 110 in the cleaning zone 106.The automatic cleaning unit 150 is installed over the OHT rails 110. Asmentioned above, the top cleaning part 152T of the automatic cleaningunit 150 is spaced apart from the OHT rails 110 by the distance D1(shown in FIG. 2). Each of the pair of side cleaning parts 152S isspaced apart from OHT rails 110. Further, each of the pair of sidecleaning parts 1525 is separated from each other by a distance D2. Insome embodiments, the distance D1 between the top cleaning part 152T andthe OHT rail 110 is greater than the height H of the wheeled trolley 142of the OHT vehicle 140 (shown in FIG. 2), and the distance D2 betweeneach of the side cleaning parts 152S is greater than the width W of theOHT vehicle 140. Accordingly, the OHT vehicle 140 is allowed to passthrough the automatic cleaning unit 150 along a moving direction asshown in FIG. 3. In some embodiments, the pair of side cleaning parts152S are movable by a linear motion guide, an X-Y table or ball screws,so that the pair of side cleaning parts 152S are adjusted to be alignedwith the wheeled trolley 142 of the OHT vehicle 140 when the OHT vehicle140 stops in the cleaning zone 106. In some embodiments, ratio of anamount of the vacuum generators 158 and an amount of the automaticcleaning units 150 is 1:1, but the disclosure is not limited thereto. Insome embodiments, each automatic cleaning unit 150 may include a vacuumgenerator 158. In some embodiments, two or more cleaning units may shareone vacuum generator 158. In some embodiments, a high efficiencyparticulate air (HEPA) filter can be adopted in the vacuum generator 158for preventing pollution to the environment, but the disclosure is notlimited thereto. In some embodiments, the vacuum generator 158 caninclude a pump, an ejector, etc. adapted to create the vacuum. In someembodiments, the piping system 159 includes a plurality of branch pipes159-1 and a main pipe 159-2. As shown in FIG. 3, the plurality of branchpipes 159-1 are connected to the top cleaning part 152T and the pair ofside cleaning parts 152S, and the main pipe 159-2 connects the pluralityof branch pipes 159-1 to the vacuum generator 158.

Referring to FIG. 4A, in some embodiments, the top cleaning part 152Tand the pair of side cleaning parts 152S can include a plurality ofholes 170. In some embodiments, the plurality of holes 170 are arrangedin an array, but the disclosure is not limited thereto. In someembodiments, the plurality of holes 170 have a diameter equal to orgreater than 2 mm, but the disclosure is not limited thereto. In someembodiments, the diameter of the plurality of holes 170 is betweenapproximately 2 mm and approximately 10 mm, but the disclosure is notlimited thereto. In some embodiments, a hole density of the plurality ofholes 170 is greater than 1 hole per cm², but the disclosure is notlimited thereto. If the hole density of the plurality of holes 170 isless than 1 hole per cm², the suction power may not be sufficient toremove the particles or debris. As shown in FIG. 4A, in someembodiments, the top cleaning part 152T and the pair of side cleaningparts 152S can include holes of different diameters and/or differentshapes. In some embodiments, the top cleaning part 152T and the pair ofside cleaning parts 152S can include holes 170 a having a rectangularshape, holes 170 b having a rectangular shape and that are larger thanthe holes 170 a, holes 170 c having a circular shape, holes 170 d havinga circular shape and that are smaller than the holes 170 c, holes 170 ehaving a star shape, or holes 170 f of a slot type. It should beunderstood that combinations of the holes 170 a to 160 f can beselectively arranged to form different patterns depending on differentcleaning requirements. For example, in some embodiments, the holesdirectly facing the wheels of the wheeled trolley 142 can have a smallerdiameter, such that at a particular level of vacuum force, greatersuction force is obtained through the smaller holes. In someembodiments, the hole diameter of the holes directly facing the wheelsof the wheeled trolley 142 may be smaller, or the hole density of theholes directly facing the wheels of the wheeled trolley 142 may begreater, such that the suction power of a portion of the cleaning parts152T and 152S directly facing the wheels of the wheeled trolley 142 is1.3 times the suction power of a portion of the cleaning parts 152T and152S not directly facing the wheels of the wheeled trolley 142. In otherembodiments, for example but not limited thereto, the holes 170 arearranged to form a pattern including different hole densities, and thehole density of a portion of the pattern directly facing the wheels ofthe wheeled trolley 142 is greater than others, and thus greater suctionpressure is provided in that portion.

Referring to FIG. 4B, the top cleaning part 152T and the pair of sidecleaning parts 152S can include a plurality of nozzles 180. In someembodiments, a density of the plurality of nozzles 180 can be greaterthan 1 nozzle per 25 cm². If the density of the plurality of nozzles 180is less than 1 nozzle per 25 cm², the suction power may not besufficient to remove the particles or debris. In some embodiments, thenozzles can be arranged in an array, but the disclosure is not limitedthereto. In some embodiments, the nozzles 180 can have different types.For example, a flat-type nozzle 180 a, an 8-hole nozzle 180 b, a 1-holenozzle 180 c and/or a nozzle with brush 180 d can be used, but thedisclosure is not limited thereto. In some embodiments, a density of thenozzles 180. In some embodiments, a length L of the nozzles 180 isbetween approximately 5 cm and approximately 30 cm, but the disclosureis not limited thereto. In some embodiments, the nozzles 180 canincludes different lengths L, and it should be understood that thelengths L of the nozzles 180 depend on different cleaning requirements.For example, in some embodiments, the nozzles 180 directly facing thewheels of the wheeled trolley 142 can have greater length L, such thatthose nozzles are nearer to the wheels and greater suction force can beprovided.

FIG. 5 is a flowchart of a method 10 for cleaning an OHT vehicle. Themethod 20 includes an operation 202, detecting a location of an OHTvehicle by a plurality of first sensors over OHT rails. In someembodiments, the first sensors are configured to define a cleaning zone.The method 20 further includes an operation 204, turning on an automaticcleaning unit installed in the cleaning zone to perform a cleaningoperation to remove particles from the OHT vehicle when the OHT vehicleenters the cleaning zone. The method 20 further includes an operation206 a, stopping the OHT vehicle to remain in the cleaning zone duringthe performing of the cleaning operation. The method 20 further includesan operation 208 a, turning off the automatic cleaning unit to stop thecleaning operation. The method 20 further includes an operation 210 a,allowing the OHT vehicle to leave the cleaning zone. The method 20 willbe further described according to one or more embodiments.

FIG. 6 is a flowchart of a method 22 for cleaning an OHT vehicle. Themethod 22 includes an operation 202, detecting a location of an OHTvehicle by a plurality of first sensors over OHT rails. In someembodiments, the first sensors are configured to define a cleaning zone.The method 22 further includes an operation 204, turning on an automaticcleaning unit installed in the cleaning zone to perform a cleaningoperation to remove particles from the OHT vehicle when the OHT vehicleenters the cleaning zone. The method 22 further includes an operation206 b, stopping the OHT vehicle to remain in the cleaning zone for apredetermined duration. The method 22 further includes an operation 208b, allowing the OHT vehicle to leave the cleaning zone after thepredetermined duration. The method 22 further includes an operation 210b, turning off the automatic cleaning unit to stop the cleaningoperation after the OHT vehicle leaves the cleaning zone. The method 22will be further described according to one or more embodiments.

Referring to FIGS. 1 to 3 again, as mentioned above, the OHT vehicles140 are operable to transport the wafer carrier through the system 100along the OHT rails 110. It is found that OHT vehicles 140 have atendency to generate particles or debris due to friction betweenwheels/rollers and the OHT rails 110. To avoid such particles fromfalling down and contaminating the tools, those particles must beremoved, and the method 20 or 22 is performed.

In some embodiments, the first sensors 154 a of each automatic cleaningunit 150 detect a location of the OHT vehicle 150 according to operation202 of the method 20. In some embodiments, when the first sensors 154 adetect one of the OHT vehicles 140 enters the cleaning zone 106, signalsare sent to the controller 160. In other words, when the first sensors154 a detect the OHT vehicle 140 approaching the automatic cleaning unit150, signals are sent to the controller 160. The controller 160instructs to turn on the automatic cleaning unit 150 according tooperation 204 of the method 20. Accordingly, the vacuum generator 158 isturned on by the controlled 160 and a cleaning operation is performed toremove the particles from the OHT vehicle 140 in the cleaning zone 106.In some embodiments, vacuum suction is generated to suck out theparticles from the wheeled trolley 142 through the top cleaning part152T, as shown in FIG. 2. In other embodiments, vacuum suction isgenerated to suck out the particles from the wheeled trolley 142 throughthe top cleaning part 152T and the pair of side cleaning parts, as shownin FIG. 3.

Further, the controller 160 instructs the OHT vehicle 140 entering thecleaning zone 106 to stop. The OHT vehicle 140 therefore remains in thecleaning zone 106 during conducting of the cleaning operation accordingto operation 206 a of the method 20. In some embodiments, the OHTvehicle 140 is stopped directly under the top cleaning part 152T, asshown in FIG. 2. In some embodiments, the OHT vehicle 140 is stoppedbetween the top cleaning part 152T and the pair of side cleaning parts152S, as shown in FIG. 3. It should be noted that a duration forperforming the cleaning operation can be adjusted depending on differentconditions. In some embodiments, the automatic cleaning unit 150, i.e.,the vacuum generator 158 of the automatic cleaning unit 150, is turnedoff to stop the cleaning operation according to operation 208 a of themethod 20, and the OHT vehicle 140 is allowed to leave the cleaning zone106 according to operation 210 a of the method 20. In addition, theautomatic cleaning unit 150, i.e. the vacuum generator 158, will beturned on the next time that the first sensors 154 a detect another OHTvehicle 140 entering the cleaning zone 106. According to the method 20,the OHT vehicle 140 leaves the cleaning zone 106 after stopping thecleaning operation.

In some embodiments, the second sensors 156 a and 156 b can be used toperform an OHT vehicle cleaning check. In some embodiments, a firstimage is captured when the OHT vehicle 140 enters the cleaning zone 106by the second sensor 156 a at the entry of the cleaning zone 106, and asecond image is captured when the vehicle 140 leaves the cleaning zone106 by another second sensor 156 b at the exit of the cleaning zone 106.The first image and the second image are then compared to check thecleaning efficacy. According to the cleaning efficacy obtained byperforming the cleaning check, parameters of the cleaning operation ofthe automatic cleaning unit 150, such as the duration for performing thecleaning operation, the vacuum force, the pattern formed by thearrangement of holes 170 of different shapes and sizes and the distancebetween the nozzles 180 and the OHT vehicle 140, can be adjusted toimprove the cleaning efficacy.

In some embodiments, the first sensors 154 a of each automatic cleaningunit 150 detect a location of the OHT vehicle 140 according to operation202 of the method 22. In some embodiments, when the first sensors 154 adetect one of the OHT vehicles 140 entering the cleaning zone 106,signals are sent to the controller 160. In other words, when the firstsensors 154 a detect the OHT vehicle 140 approaching the automaticcleaning unit 150, signals are sent to the controller 160. Thecontroller 160 instructs to turn on the automatic cleaning unit 150according to operation 204 of the method 22. Accordingly, the vacuumgenerator 158 is turned on by the controller 160 and a cleaningoperation is performed to remove the particles from the OHT vehicle 140in the cleaning zone 106. In some embodiments, vacuum suction isgenerated to suck out the particles from the wheeled trolley 142 throughthe top cleaning part 152T, as shown in FIG. 2. In other embodiments,vacuum suction is generated to suck out the particles from the wheeledtrolley 142 through the top cleaning part 152T and the pair of sidecleaning parts, as shown in FIG. 3.

Further, the controller 160 instructs the OHT vehicle 140 entering thecleaning zone 106 to stop. The OHT vehicle 140 remains in the cleaningzone 106 for a predetermined duration according to operation 206 b ofthe method 22. In some embodiments, the predetermined duration can be,for example but not limited thereto, 20 minutes. In some embodiments,the OHT vehicle 140 is stopped directly under the top cleaning part152T, as shown in FIG. 2. In some embodiments, the OHT vehicle 140 isstopped between the top cleaning part 152T and the pair of side cleaningparts 152S, as shown in FIG. 3. In some embodiments, the OHT vehicle 140is allowed to leave the cleaning zone 106 according to operation 208 bof the method 22. Further, when the first sensors 154 b detect the OHTvehicle 140 leaving the cleaning zone 106, a signal is sent to thecontroller 160, and the automatic cleaning unit 150, i.e., the vacuumgenerator 158 of the automatic cleaning unit 150, is turned off by thecontroller 160 to stop the cleaning operation according to operation 210b of the method 22. In addition, the automatic cleaning unit 150, i.e.the vacuum generator 158, will be turned on the next time that the firstsensors 154 a detect another OHT vehicle 140 entering the cleaning zone106. According to the method 22, the cleaning operation is stopped afterthe OHT vehicle 140 leaves the cleaning zone 106. In some embodiments,it can be assured that particles will not fall back onto the OHT vehicle140.

In some embodiments, the second sensors 156 a and 156 b can be used toperform an OHT vehicle cleaning check. In some embodiments, a firstimage is captured when the OHT vehicle 140 enters the cleaning zone 106by the second sensor 156 a at the entry of the cleaning zone 106, and asecond image is captured when the vehicle 140 leaves the cleaning zone106 by another second sensor 156 b at the exit of the cleaning zone 106.The first image and the second image are then compared to check thecleaning efficacy. According to the cleaning efficacy obtained byperforming the cleaning check, the predetermined duration or parametersof the cleaning operation of the automatic cleaning unit 150, such asthe vacuum force, the holes 170 of different shapes and sizes and thedistance between the nozzles 180 and the OHT vehicle 140, can beadjusted to improve the cleaning efficacy.

In some embodiments, every time the OHT vehicles 140 enter one of theautomatic cleaning units 150, the OHT vehicles 140 are cleaned. Since aplurality of automatic cleaning units 150 are used in the system 100,the OHT vehicles 140 can be cleaned many times and thus the duration oftime required for performing the cleaning operation in the method 20 orthe predetermined duration in the method 22 can be further reduced whilethe cleaning efficacy is still improved due to the plurality ofautomatic cleaning units 150.

In some embodiments, the controller 160 can select some of the automaticcleaning units 150 to perform the cleaning operation. Therefore, the OHTvehicles 140 will be cleaned only when entering the selected automaticcleaning units 150. Accordingly, downtime can be further reduced.

In some embodiments, the controller can select some of the OHT vehicles140 to enter the automatic cleaning units 150 when the cleaning checkreveals that particles still remain on those OHT vehicles 140. Those OHTvehicles 140 are therefore recognized as non-clean, and assigned toenter the automatic cleaning units 150 again.

The present disclosure provides an automatic cleaning unit, a systemincluding the automatic cleaning units, and a method for cleaning theOHT vehicles. The automatic cleaning units can be to function on the OHTrails. The automatic cleaning unit includes sensors to detect the OHTvehicles and thus can be automatically turned on by the controller whenthe OHT vehicles approach the cleaning unit and a cleaning operation isperformed. The automatic cleaning unit can also be automatically turnedoff by the controller when the when cleaning operation is stopped orafter the OHT vehicles leave the automatic cleaning zone. Further, theautomatic cleaning unit includes vacuum cleaning parts for removingparticles from the top and sides of the wheeled trolley of the OHTvehicles.

According to the automatic cleaning units and the system including theautomatic cleaning units, the cleaning operation is performedautomatically without manual involvement. In some embodiments, manualcleaning requires more than one hour. In some embodiments, since theautomatic cleaning units are installed along the OHT rails, and the OHTvehicles can be cleaned many times along the OHT rails, a duration forperforming the automatic cleaning operation can be reduced to less than20 minutes while the cleaning efficacy is still improved. Further, thecleaning efficacy can be improved by adjusting the duration forperforming the cleaning operation, and the parameters of each automaticcleaning unit. In some embodiments, the quantity of the automaticcleaning units can be adjusted depending on the cleaning requirements ofFAB or a length of the intra-bay loop and the inter-bay loop. In someembodiments, in a system having more than 8,000 OHT vehicles, a cycletime for cleaning all of the OHT vehicles can be reduced from 3 monthsto one week. It is found that since the frequency for cleaning the OHTvehicles is increased, fewer particles may be generated and disposedover the wheeled trolley, and thus the duration for performing thecleaning operation can be further reduced. Additionally, by turning onthe vacuum generator only when the OHT vehicle is in the cleaning zone,power consumption is reduced.

In some embodiments, a system for a semiconductor fabrication facilityis provided. The system includes a network of OHT rails, a plurality offirst sensors disposed on the network of OHT rails, and a plurality ofautomatic cleaning units. The plurality of first sensors are configuredto define a plurality of cleaning zones, and to detect locations of aplurality of OHT vehicles movably mounted on the network of OHT rails.The automatic cleaning units are installed in the cleaning zones. Theautomatic cleaning units are separated from each other by a distance. Insome embodiments, each of the plurality automatic cleaning units isinstalled over the network of OHT rails and separated from the networkof OHT rails to allow the plurality of OHT vehicles to pass throughalong a moving direction.

In some embodiments, a method for cleaning an OHT vehicle is provided.The method includes the following operations. A location of an OHTvehicle is detected by a plurality of first sensors over OHT rails. Thefirst sensors are configured to define a cleaning zone. An automaticcleaning unit installed in the cleaning zone is turned on to perform acleaning operation to remove particles from the OHT vehicle when the OHTvehicle enters the cleaning zone. The automatic cleaning unit is turnedoff to stop the cleaning operation.

In some embodiments, a system for a semiconductor fabrication facilityis provided. The system includes a network of OHT rails, a plurality offirst sensors on the network of OHT rails, and a plurality of automaticcleaning units. The plurality of first sensors are configured to definea plurality of cleaning zones, and to detect locations of a plurality ofOHT vehicles movably mounted on the network of OHT rails. The automaticcleaning units are installed in the cleaning zones. Each of theplurality of automatic cleaning units includes a vacuum generator, acontroller, and a top cleaning part. The controller is in communicationwith the plurality of first sensors and the vacuum generator. The topcleaning part is installed on the OHT rails in the cleaning zone andcoupled to the vacuum generator.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A system for a semiconductor fabricationfacility, comprising: a network of OHT rails; a plurality of firstsensors on the network of OHT rails, wherein the plurality of firstsensors are configured to define a plurality of cleaning zones and todetect locations of a plurality of OHT vehicles movably mounted on thenetwork of OHT rails; and a plurality of automatic cleaning unitsinstalled in the cleaning zones, wherein the plurality of automaticcleaning units are separated from each other by a distance, and each ofthe plurality automatic cleaning units is installed over the network ofOHT rails and spaced apart from the network of OHT rails to allow theplurality of OHT vehicles to pass through along a moving direction. 2.The system of claim 1, wherein the distance between two of the pluralityof automatic cleaning units is between approximately 500 m andapproximately 3000 m.
 3. The system of claim 1, wherein each of theplurality of automatic cleaning units comprises a top cleaning partdisposed over the network of OHT rails in the cleaning zone.
 4. Thesystem of claim 3, wherein the each of the plurality of automaticcleaning units comprises a pair of side cleaning parts disposed at twosides of the network of OHT rails in one of the plurality of cleaningzones and coupled to the top cleaning part.
 5. The system of claim 4,wherein the top cleaning part and the pair of side cleaning partsrespectively comprise a plurality of holes or a plurality of nozzles. 6.The system of claim 1, further comprising at least a second sensordisposed over the network of OHT rails, wherein the second sensor isconfigured to perform an OHT vehicle cleaning check.
 7. A method forcleaning an OHT vehicle, comprising: detecting a location of an OHTvehicle by a plurality of first sensors over OHT rails, wherein theplurality of first sensors are configured to define a cleaning zone;turning on an automatic cleaning unit installed in the cleaning zone toperform a cleaning operation to remove particles from the OHT vehiclewhen the OHT vehicle enters the cleaning zone; and turning off theautomatic cleaning unit to stop the cleaning operation.
 8. The method ofclaim 7, wherein the cleaning operation is performed by vacuuming. 9.The method of claim 7, further comprising: stopping the OHT vehicle toremain in the cleaning zone during the performing of the cleaningoperation; turning off the automatic cleaning unit to stop the cleaningoperation; and allowing the OHT vehicle to leave the cleaning zone. 10.The method of claim 7, further comprising: stopping the OHT vehicle toremain in the cleaning zone for a predetermined duration; allowing theOHT vehicle to leave the cleaning zone after the predetermined duration;and turning off the automatic cleaning unit to stop the cleaningoperation after the OHT vehicle leaves the cleaning zone.
 11. The methodof claim 7, further comprising performing an OHT vehicle cleaning checkby at least a second sensor.
 12. A system for a semiconductorfabrication facility, comprising: a network of OHT rails; a plurality offirst sensors on the network of OHT rails, wherein the plurality offirst sensors are configured to define a plurality of cleaning zones andto detect locations of a plurality of OHT vehicles movably mounted onthe network of OHT rails; and a plurality of automatic cleaning unitsinstalled in the cleaning zones, wherein each of the plurality ofautomatic cleaning units comprises: a vacuum generator; a controller incommunication with the plurality of first sensors and the vacuumgenerator; and a top cleaning part installed over the OHT rails in thecleaning zone and coupled to the vacuum generator.
 13. The system ofclaim 12, wherein each of the plurality automatic cleaning units isinstalled over the network of OHT rails and spaced apart from thenetwork of OHT rails to allow the plurality of OHT vehicles to passthrough along a moving direction.
 14. The system of claim 12, whereinthe plurality of automatic cleaning units are separated from each otherby a distance.
 15. The system of claim 14, wherein the distance betweentwo of the plurality of automatic cleaning units is betweenapproximately 500 m and approximately 3000 m.
 16. The system of claim12, wherein the controller turns on the vacuum generator to perform avacuum cleaning operation through the top cleaning part when theplurality of first sensors detect the OHT vehicle entering the cleaningzone.
 17. The system of claim 12, wherein the each of the plurality ofautomatic cleaning units comprises a pair of side cleaning partsdisposed at two sides of the network of OHT rails in one of theplurality of cleaning zones and coupled to the top cleaning part. 18.The system of claim 17, wherein the top cleaning part and the pair ofside cleaning parts respectively comprise a plurality of holes.
 19. Thesystem of claim 17, wherein the top cleaning part and the pair of sidecleaning parts respectively comprise a plurality of nozzles.
 20. Thesystem of claim 12, further comprising at least a second sensor disposedover the network of OHT rails, wherein the second sensor is configuredto perform an OHT vehicle cleaning check.